1. Field of the Invention
The present invention relates to an USB application device, more specifically, to a miniaturized USB application device.
2. The Related Art
Because Universal serial bus (USB) interface has advantages of high convenience, high compatibility and high transmission speed, it is widely applied to various electronic devices such as personal computers, MP3 players, MP4 players, external storage devices, laptops, flash storage devices, etc. Hence, USB interface becomes one of the standard interfaces of the electronic devices.
A conventional USB compatible application apparatus is disclosed in U.S. Pat. No. 7,165,998. The USB compatible application apparatus has a printed circuit board (PCB) to be a carrying board inside of a connector. A top surface of the PCB carrying board includes a plurality of terminals. A board bottom sandwich is formed between a bottom surface of the PCB carrying board inside the connector and a covering shell of the connector. At least one electrical element is fixed on the bottom surface of the PCB carrying board inside the connector.
Therefore, the present invention can shorten the length of the USB compatible application devices or improve the working efficiency of the USB compatible application device.
Furthermore, the board bottom sandwich has at least one supporting structure, front end protection layer, and a combination thereof capable of connecting to the PCB carrying board. Hence, the supporting structure can fix the size of the board bottom sandwich and prevent the board bottom sandwich from transforming by the unexpected outer force. The front end protection layer can protect the electrical element located inside the board bottom sandwich and meanwhile efficiently strengthen the structure of the board bottom sandwich.
However, the covering shell is selectively made of a non-metal material, e.g. plastic, plasticity steel, or polymer. The strength of the non-metal material covering shell is weaker than metal shell. Therefore, the board bottom sandwich is arranged at the bottom of the supporting structure and the front end protection layer for improving structure.
Moreover, the non-metal material covering shell can not comply with the electrostatic discharge (ESD) testing standard specification. Therefore, the USB compatible application apparatus can not comply with the USB standard specification. Because the electrical element is located on the bottom surface of the PCB carry board, the location of the supporting structure inside the board bottom sandwich must avoid the location of the electrical element. However, it is complex to design the location of the electrical element and the supporting structure at the same layer.